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Sound Perception

Sound and its Perception, Acoustics, Decibels

QuestionAnswer
to-and-fro motion of an object is defined as oscillation
vibration transferred from air particle to air particle is usually called sound
disturbance of molecules that propagates (moves) through a medium is sound
substance through which sound travels, such as air, water, steel, bone is called a medium
movement of a disturbance of molecules through a medium is called propagation of sound
molecules displaced a very small distance from where they want to be (equilibrium position) is a disturbance of molecules
this is where the net force is zero equilibrium position
a kind of vibration where the oscillations repeat themselves at same rate over and over again like a pendulum is called simple harmonic motion
when oscillation dies down the dying of vibrations over time is called dampening
if you increase volume you increase pressure (like air in tire)
if you decrease volume you decrease pressure
state of lower than ambient pressure (pressure is maximally negative) rarefaction
state of positive air pressure or molecules pushed together creating more dense space is called compression (condensation)
a sudden short sound that doesn't last long is known as a transient sound (ex: slamming of door or an unvoiced sound such as "sss...") or impulse sound
when sound source is farther away and its a few seconds before you hear the sound, this is because speed of light is faster than sound
speed of sound is related to elasticity and density of the medium
speed of sound is equal to C (speed of sound)
the restorative force, which can be thought of as the ability of a substance to resist deformation is called elasticity (E)
the amount of mass per unit volume is known as density (D)
broccoli has greater _______ than the Oregonian rubber band, because it won't deform as easily elasticity
the greater the elasticity the greater the speed of sound
increase elasticity increase C
increase density decrease C
air is less dense as we increase temperature
as gas expands density decreases
speed increases with temperature because gas expands as temperature increases (and molecules move quicker)
steel and water are more ______ than air dense
helium is less _____ than air, so sound travels ______ through it than air dense, faster
CO2 is more ______ than air, so sound travels ________ through it than air dense, slower
water and steel are more dense than air, so sound travels _______ this is because of elasticity (the dominant factor) faster
compressions and rarefactions move from ________ to ______ sound source to reciever
vibration that repeats itself periodic vibrations (ex: guitar string or "aaaa")
vibration that doesn't repeat itself aperiodic vibration (ex: door slamming, "sssss")
single complete execution of a periodically repeated phenomenon cycle
measure of magnitude of a sound/vibration amplitude
time it takes to complete one cycle period
number of cycles per second frequency
how fast something is vibration is known as cps=cycles per second
F= 1/period (1/T) (Unit: Hz)
T= 1/F (Unit: sec)
velocity= displacement/time (30miles/1hr)
pressure= force/area
the greater the force, the greater the _______ pressure
psi stands for pounds per square inch
in the metric system the unit for force is Newton's
1 Pa= N/m2
Force= mass times acceleration (F=ma)
amount of force required to cause a mass of 1 Kg to accelerate to 1 meter/squared sec (1m/s2) is Newton
the distance btwn successive condensations and rarefactions is the wavelength
the faster the speed of sound the _______ the wavelength (lower frequency) larger
the smaller the wavelength the higher the frequency
wavelength= speed of sound/frequency (wavelength=c/f)
2 sinusoids with same frequency, only _______ changes and gets larger/higher amplitude
hearing nothing, like noise cancellation headphones is called total cancellation
different frequencies combined together make a complex waveform
any waveform that is not a sinusoid is a complex waveform
wave that repeats itself periodic waveform
even integral number multiples of a frequency harmonic
the largest common multiple of a series of sinusoids fundamental frequency
With frequencies of 150Hz, 250Hz, 350Hz what would the fo be and the 2nd and 3rd harmonic? fo=50 (1st harmonic), 2nd harmonic=100, 3rd harmonic=150
Given frequencies: 125, 250, 375, 500Hz what is the fo? and the H3? fo=125Hz (Ist harmonic), H3=375Hz
300Hz is or below is cancelled-the difference in pitches, this is called the case of the missing fundamental
Fo of a mans voice is= 100Hz
Fo of a females voice is= 175-200Hz
a straight line of a sinusoid that shows what frequencies are present is known as a spectrum
mathematical procedure that coverts and breaks waveform down by means of frequencies (from time domain>frequency domain) Fourier Analysis
most vibrations are aperiodic
top of the peaks on the spectrum graph are known as formants (each vowel has it's own pattern of formants, so when we change shape in tongue, they change frequency)
the faintest sound human ear can detect 20 microPa=.00002Pa (very small change in pressure)
the loudest sound human ear can detect 20,000,000 microPa=20Pa
the power to which 10 has to be raised, to equal that number log10
log10^1= 0
log10^10= 1
log10^1000= 3
log10^1,000,000=log10^6= 6
log10^4=4= log10^10,000
P1/Po Pressure/Reference Pressure
SPL stands for Sound Pressure Level
the logarithm formula we use is: 20logP1/Po (Po=.00002 Pa, standard measure point for SPL) we use this to calculate the dB SPL or dB of the pressure of a sound or sounds.
The pressure of sound A=.035 Pa. The pressure of sound B=.0075 Pa. How many dB is sound A above sound B? 13.38 dB (not dB SPL, because need 20 mPa=.00002 Pa)
The pressure of a sound is .44 Pa. How many dB SPL is this? 86.85 db SPL
If sound A is twice the pressure of sound B, there is a ____ dB difference. 6
Pressure of sound a IS 10 times the pressure of sound B. How many dB is A above B? 20 dB
Pressure of sound A= .00002 Pa and pressure of sound B= .00002 Pa. How many dB is A relative to B? 0 dB SPL (As long as they're the same, you get 0 dB)
If you combine dB from multiple sound sources, such as 80 dB SPL and 80 dB SPL, you get a _____ dB SPL increase. 86 dB SPL (80 dB SPL + 6 dB)
if waveform of 2 sounds are identical aka same frequency, you get a doubling of sound ______ pressure
There are 2 tractors in a field both with 90 dB SPL, one starts its engine and then the other. What is the combined dB SPL? 93 dB SPL, because free field, no reflection of buildings or trees because empty space outside.
80 dB SPL + 6 dB= 86 dB SPL
Two or more dB values of different sounds can look the same, but are not necessarily the same unless they have the same ______ ________ reference pressures
power=energy flow= watts
intensity=energy flow/unit area= watt/m2
faintest sound intensity (at 20mPa pressure)= 10^-12 w/m2
anytime you have fraction such as .42, the answer is going to be negative
energy flow, energy expanded per unit time watts is Power
energy flow per unit area aka power speed over a given area is Intensity
Power/area= watt/m2
Unit of measurement for dB with intensity is I1/Io and has a unit value of dB IL (as long as ration of 2 intensities)
opposition to energy flow impedance
energy lost in the form of heat resisitance (friction)
energy is stored reactance
if you have a spring that is opposing and continues to compress you have more and more potential energy created, which is then stored in the string, which is called _______ _______ compliant reactance (opposition to force, potential energy stored
opposition to force, energy stored in motion, kinetic is mass reactance
what are the two types of impedance? resistance and reactance
what are the two types of reactance? mass reactance and compliant reactance
When P1 negative (this is because the log of a fraction is negative)
P1=Po there are ____ decibels. zero (because the logarithm of 1 is zero)
If the pressure of one sound source is twice that of another, it is ___ dB greater than the second sound. 6 db (This is because 20log10^2=6dB)
combining two sounds with exactly the same waveforms will result in ___ the pressure of one sound alone. twice
If the time waveforms of two sounds are not equal, combining the sounds will not _____ the pressure. For example, two machines, each producing 70 dB SPL will together produce 73 dB SPL. That is, there will be an increase of only __ dB. double, 3 dB
dB SPL - dB = dB SPL
dB SPL + dB = dB SPL
dB SPL - dB SPL = dB
If Po is not .00002 Pa, then the unit is not SPL
Express the number 10,000,000,000 in exponential form. 10^10
What is the logarithm base 10 of 10,000,000,000? log10=10
T/F Zero dB means that no sound is present. False
T/F 20mPa corresponds to .00002 Pascals. True
T/F The unit of intensity is the watt. False, it is watt/m2. watt is the unit of power.
T/F For a given sound source, sound pressure in a room depends on the size of the room. True
Created by: rcheek